Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual é a capacidade para uma instalação aberta em 1956?
 ###Tabelas: CREATE TABLE scholarly_journals (scholarly_journals_id AUTO_INCREMENT PRIMARY KEY, ISSN VARCHAR, Language VARCHAR, Country VARCHAR, Frequency VARCHAR, Publication range VARCHAR, Status VARCHAR, Document Type VARCHAR) CREATE TABLE england_in_west_indies (england_in_west_indies_id AUTO_INCREMENT PRIMARY KEY, Date VARCHAR, Home captain VARCHAR, Away captain VARCHAR, Venue VARCHAR, Result VARCHAR) CREATE TABLE human_resource_development (human_resource_development_id AUTO_INCREMENT PRIMARY KEY, Region VARCHAR, Physician (GP & specialist) INT, Physician : Population Ratio VARCHAR, Health Officer INT, HO : Population Ratio VARCHAR, All Nurses INT, Nurse : Population Ratio VARCHAR, Mid-wives VARCHAR, Mid Wife: Population Ratio VARCHAR, HEW* VARCHAR) CREATE TABLE characters_casts_and_recordings (characters_casts_and_recordings_id AUTO_INCREMENT PRIMARY KEY, Character VARCHAR, Original Broadway performer VARCHAR, Original Australian performer VARCHAR, Original West End performer VARCHAR, 2005 World AIDS Day Benefit Dream Cast VARCHAR) CREATE TABLE current_prisons (current_prisons_id AUTO_INCREMENT PRIMARY KEY, Facility VARCHAR, Location VARCHAR, Year Opened VARCHAR, Major Facility VARCHAR, Population Gender VARCHAR, Capacity INT, Custody Level(s) VARCHAR)  
SELECT COUNT Capacity FROM current_prisons WHERE Year Opened = 1956